[Lua] Using Tick Bus - o3de/o3de GitHub Wiki

Polling

When you need to do something every frame, the TickBus is what you will need to use. The TickBus will notify every component that is subscribed to it when a new frame has occured. The component will also receive information such as deltaTime: the time in seconds since the last frame.

local Ticking = {}

function Ticking:OnActivate()
  self.tickHandler = TickBus.Connect(self)
end

function Ticking:OnDeactivate()
  self.tickHandler:Disconnect()
  self.tickHandler = nil
end

function Ticking:OnTick(deltaTime, timePoint)
  Debug.Log("I am printing every frame! Time since last frame in seconds: " .. deltaTime)
end

return Ticking

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Breakdown

Connecting to TickBus

When the component activates, we use Connect to subscribe to TickBus events. We need a variable self.tickHandler to store a reference so that we can unsubscribe from the TickBus. You can name this variable whatever you like.

function Ticking:OnActivate()
  self.tickHandler = TickBus.Connect(self)
end

Receiving Tick Events

To receive TickBus events you simply need to have correctly named TickBus event functions, which will be called automatically as long as your component is subscribed to the TickBus. Any parameters you include will also be populated when the function gets called. Use the Classes Reference in LuaIDE to find the available events and parameters.

function Ticking:OnTick(deltaTime, timePoint)
  Debug.Log("I am printing every frame! Time since last frame in seconds: " .. deltaTime)
end

Disconnecting from TickBus

To unsubscribe from TickBus events, use Disconnect on the reference stored during the connection process. It is not strictly necessary to Disconnect or set variables to nil when a component deactivates, but it is considered best practice. It is safe to use Disconnect on a handler that is already disconnected but not when it is nil.

function Ticking:OnDeactivate()
  self.tickHandler:Disconnect()
  self.tickHandler = nil
end

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Additional Resources

• TickBus.h source code link